Some temperature regulators are used for the temperature control of the reaction tube in a heat treatment apparatus such as a heat oxidation apparatus in a semiconductor fabrication process. The heat oxidation apparatus is adapted to generate an oxidation film on a wafer put in a reaction tube while supplying necessary gas therein. The inside of the reaction tube is divided into plural zones each provided with a heater and a temperature sensor, although these zones are spatially communicated with each other. The detection result of each temperature sensor is inputted to the temperature regulator having a microcomputer and the like.
The temperature regulator controls the temperature of the corresponding zone by controlling each heater in accordance with the detection result of the corresponding temperature sensor. These zones of the reaction tube are thermally open to each other, so the amount of heat from a heater in a zone affects or causes interference with a temperature sensor in another zone. Such interference causes remarkable variations in temperature between each zone especially at the time of transient or in the presence of disturbance, making it difficult to perform uniform temperature control of each zone. The interference also makes it uneasy to control the different zones at different target temperatures.
In view of these, the present invention has a main object of providing a controller capable of keeping the control target under desired physical conditions by reducing the interference, even if the control target has the interference.